1. Field of the Invention
The present invention relates to an organic light emitting display (OLED) and method of fabricating the same and, more particularly, to an OLED including a hole acceleration layer between a hole injection layer and a hole transport layer.
2. Discussion of the Background
Generally, an OLED is a thin, lightweight self-emissive display device that has simple components and may be fabricated using a simple process. Also, the OLED may have high resolution and a wide viewing angle, which enables high quality moving images and color purity. Further, since the OLED may operate at low power and voltage, it is appropriate for mobile devices.
In a conventional OLED structure, a pixel electrode is arranged on a substrate, an organic layer including an emission layer (EML) is arranged on the pixel electrode, and an opposite electrode is arranged on the organic layer. The organic layer may further include a hole injection layer (HIL) and a hole transport layer (HTL) between the pixel electrode and the EML, and it may also include an electron transport layer (ETL) and an electron injection layer (EIL) between the EML and the opposite electrode.
An OLED as described above operates on the following principle. Applying a voltage between the pixel electrode and the opposite electrode injects holes from the pixel electrode through the HIL and HTL into the EML, and injects electrons from the opposite electrode through the EIL and ETL into the EML. The holes and electrons then recombine in the EML to generate excitons, which emit light while transitioning from an excited state to a ground state.
Generally, since a top-emitting OLED utilizes optical resonance, the pixel electrode, the HIL, and the HTL are typically formed to a thickness that is equivalent to a wavelength range. The HIL facilitates hole injection from the pixel electrode when it is an anode, thereby improving power consumption efficiency and the OLED's life span. Also, the HTL, which has high hole mobility, allows holes to be easily transported and binds electrons in an emission region so as to increase the likelihood of generating excitons. In order to realize National Television System Committee (NTSC) chromaticity coordinates, the OLED typically includes an HIL and an HTL, each of which has an appropriate thickness. However, if the HIL and HTL are formed to the appropriate thickness, a driving voltage is increased due to the HIL's relatively low hole mobility, thus resulting in high power consumption.